Solvent extraction in successive operations



Oct. 19, 1937. w, F, -FARAG'HER 2,095,972

` 'soLvENT ExTnAcTIoN In succisssxvs oPEnA'uons Filed uarcrin 1934 2 sheets-sheet 1 wimax ffm/ffy ATTCRNEY Oct. 19, 1937. w. F. FARAGHER 2,095,972

SOLVENT EXTRACTION IN SUCCESSIVE OPERATIONS 2 Sheets-Sheet 2 Filed March 7, 1934 Seu/zd Second 6121462' fafff/ue 7b 520mg@ f 7b sia/'eye saire/zi saire/zt nare/y fecal/ely INVENTOR v ATTORNEY Patented Oct. 19, 1937 soLvEm` Ex'raAc'rioN 1N sUccEssrvE orEnATIoNs Warren F. Faragher, Woodbury, N. J., assigner to I Ioudry Process Corporation, Dover, Del., a corporation of Delaware Application March?, 1934, Serial No. I714,417

l4 claims. (ci.V 19e- 13) This invention relates to the production of rai'- flnates and/or extracts from composite materials,

especially mineral oils, and distillates, fractions, blends, products and residues thereof. More particularly, it concerns the manufacture of lubricating oils, insulating oils, and other final orintermediate products requiring the selective concentration of certain favorable components and the suppression and/or removal of certain undesirable components.

In solvent refining of lubricating stocks the reliner usually iinds that he must .sacrice high yields if he is to produce a raffinate of the highest quality possible of realization with such processes. On the other hand, if he is to hold his production costs, per unit of marketable product, to a reasonable figure, he frequently iinds it necessary to sacrifice quality for the sake of a better yield.

One object of the invention is to devise ways and means for eifecting a more complete segregaobject is to secure both high yield and -high quality of product. Still another object is to change the temperature of operation to more 'favorable 3o the detailed description which follows.

` The invention involves the use of two solvents in distinctand successive operations, rather than concurrently. One solvent is iirst applied to the starting material and then the other solvent is used on one of the products or extracts from the rst solvent operation. For example, in the treat- Y ment of a lubricating stock, a selective naphthenic solvent may be used to produce a high viscosity index raiilnate, the other extract or reject being then subjected to the action of'a second or paraiinic solvent to strip thesame of entrained or absorbedparains thereby to secure a high total yield of parafnic constituents suitable for 45 lubricants.` The lighter extract or raffinate from the second solvent treatment, comprising paraffns and some of the naphthenes most easily dissolved by the parainic solvent, may be inferior to the first railinate in quality but is still able to 50 meet presentday standards for automobile and other lubricants. Recycling or recirculating a partof one of the extracts or group of compo- I nents may be resorted to in either or both of the above successive solventoperations, to control the 5 relative parainicity and naphthenicity of hydroranges. Still other objects will be apparent from' stages.v In the iirst'solvent operation, the fresh l ly. at points illustrated hereinafter, whenever it is advantageous or economical by reason of a still more complete separation of components. Inl certain instances recycling favorably aifects the temp perature or range of temperature where the sepa- 5 rating action takes place.

In order to illustrate the invention and the manner of its use, concrete embodiments thereof are diagrammatically indicated in the accompanying drawings, in which: 10

Fig. 1 indicates solvent treatment in successive operations by the use of` packed towers;

Fig. 2 indicates multiple stage solvent treatment in successive operations; and

Figs. 3 and 4 are similar to Figs. 1 and 2, re- 15 spectively, but lindicating methods of recycling.

In the countercurrent packed tower or special tray towerA system indicated in Fig. 1, the charge oil is admitted into the lower end of the first tower, while a solvent for naphthenes and aromatics, 20 such as phenol, nitrobenzene, certain chlorine de-l rivatives of organic` compounds, especially dichlorethyl-ether, or the like, is admitted at the Y upper end ofthe tower and passes therethrough countercurrently to the charge oil. The upper extract or raiinate passes 01T at the top to storage and to solvent recovery, while the lower extract containing the solvent is withdrawn at the bottom of the tower and is passed directly to the top of a second packed or vspecial tray tower, Where it moves ycountercurrent to a solvent for parailns, such as propane, butane, straight run light naphthas, or the like, admitted at the lower end of the second tower. The paraiiinic solvent strips the extract from the first packed tower of most if not all of the desirable components, the latter passing from the top of the second packed tower as a second upper extract or raiiinate to be kept in storage or sent to solvent recovery. The iinal or second lower extract is withdrawn from the bottom of the second packed tower for stor- Vage or sent to solvent recovery.

charge oil is subjected to the action of a solven'tfor naphthenes and aromatics such as specied in connection with Fig. 1. The charge oil is directed to mixer lVI-l of'the rst mixing and separating stage, While the solvent goes from storage iirst to mixer M4 of the '.tourth mixing and separating stage. Thus charge oil, mixed with thrice used solvent'and extract admitted by line E-3 from the bottom of separator S-2 of the second mixing stage, passes to the rst mixing and reiining stage. The upper layer or raffinate from separator S-I passes to mixer M-2 of the second mixing and separating stage along with twice used solvent and extract passing by' line E-Z from the bottom of separator S--3 of the third mixing and separating stage. The upper separated layer or ramnate passes from separator S-Z by line R2 to mixer 'M -3 of the third mixing and separating stage along with once used solvent and extract passing from the bottom of separator S--I of the fourth mixing stage by line E-I. Upper layer or raiiinate from separator S-3 of the third mixing stage passes by line R--3 to mixer M- of the fourthmixing stage together with fresh naphthenic solvent from storage. The final upper layer extract or raffinate passes from separator S-- of the fourth mixing and separating stage directly to first rafnate storage, whence it may be removed for solvent recovery. The nal lower layerextract, composed largely of solvent andthe undesirable components of the charge oil, passes from the bottom of separator S-l of the first separating stage by line E-I to iirst extract storage. lThis completes the iirst solvent operation.

This final extract from the first operation, which may be called for convenience the iirst extract, is then subjected coimtercurrently in a similar group of stages to the action or suitable solvent for paralnes, including any of those mentioned in connection with Fig. l. Since the movement vof the charging stock and of the solvent in the second operation conforms to that already described in connection with the iirst operation, a detailed recitation of the same is unnecessary, but, to make it clear, the same reference characters are applied to the elements of the second operation as for the rst operation, xcept that the letters are primed. In this second operation, the nal or first extract of the iirst operation is stripped o! the desirable com-- ponents entrained or retained therein, with the result that a nal or second raffinate is withdrawn by line R'4 from the fourth or unal mixing and separating stage of the second operation. This second raffinate may be somewhat inferior in quality to the raffinate from the rst operation, due to the possible inclusion of a larger quantity of naphthenic or aromatic components.

Figs. 3 and 4 indicate ways in which recycling may be utilized in both countercurrent tower contact systems and multiple stage mixing and separating systems, for the purpose of efiecting a still more complete separation of the desirable and undesirable components. It is to be understood that recycling may be used in such systems in either theiirst solvent operation or in the second solvent operation, or in both operations, as may be found to be most advantageous and economical. Fig. 3 indicates by a 4heavy black line selective withdrawal of all or a part o! the iirst lower extract and discharge of theghie into theV upper. end of the first packed tower at a point somewhat below the inlet for fresh naphthenic solvent. In the second solvent operation of the system shown in Fig. 3, recycling is effected (see the heavy black line) by taking all or a selected quantity of the second upper extract or railina'te and discharging the same into the lower end of the second packed tower at a point somewhat above the inlet for the fresh parainic solvent.

For the stage solvent system indicated in Fig. 4, recycling may be effected by sending all or a selected portion of the final extract by line C-I, indicated in heavy black, to join line E-I which conducts once used solvent and extract from separator S-4 to mixer M--3 of the third mixing and separating stage. For the second solvent operation, the rainate is recycled rather than the extract, line C'-l (also in heavy black) conducting all or a selected part of the final or second raffinate from line R-4 to join the lines4 leading to mixer M'-I of the first mixing and separating stage, this recycled rainate being mingled with fresh charge comprising the iinal extract of the iirst solvent operation, together with the extract Withdrawn fromthe bottom of separator S'2 of the second mixing and separating stage.

For systems such as indicated in Figs. 3 and 4, it is preferable to recycle completely until products of the desired quality are obtained and thereafter to elect only a partial recycling while the remainder of the products capable of being recycled are withdrawn, intermittently or continuously, from the system. In certain instances, recycling makes possible a raising of the temperature at which the components separate with 'the desired composition thereby lowering the cost of refrigeration.

It is to be understood that the terms desirable and undesirable are used herein in a relative rather than in a limiting sense, and in order t0 make the terminology conform to common usage in the industry. Both or all of the extracts or groups of components are desirable in the sense that they are convertible into valuable finished products.

While my invention, in referring to the introduction or recycling of strongly naphthenic hydrocarbons in one extraction zone, or equivalent, and to the introduction of strongly paraiiinic components in a second extraction zone, or equivalent, is particularly illustrated by recycling products of the process, yet it will be understood that my invention is not to be limited by this specific, preferred illustration but is meant to cover equivalent operations. For example, instead of recirculating particular products of my process, this invention comprehends introducing into the reaction zones, from outside sources, liquids respectively of the approximate composition of recycled liquids hereinabove described, thereby to improve the yield and quality of desired products.

I claim as my invention:

1. In the art of separating a hydrocarbon charging material into desirable and undesirable components by the action of solvents, the operative process which comprises acting on the charging material with a solvent for the undesirable components, removing the desirable components thus separated, then subjecting the solvvent mixture containing undesirable components from the iirst solvent operation to the action of a solvent for the desirable components thereby to strip said mixture of any desirable components retained therein, and during the second solvent operation altering naphthenicity of hydrocarbon material being extracted by introducing a liquid, of at least approximately the composition oi.' the desirable components separated therein, into the zone of the relative paraiiinicity and said second extraction operation at a point remote from .the point o! withdrawal of desirable components therefrom so that the said liquid contacts the hydrocarbon material being extracted in said second. solvent operation and moves in counteriiow relation with the same.

2. In the art of separating a viscous hydrocarbon oil charge into fractions which are relativelymore paralnic and more naphthenic than the original charge, the process which comprises acting on the charge with a solvent for naphthenesin a counter ow operation in a first extraction zone to separate out an extract fraction and a raiiinate fraction. recycling a portion of the extract fraction into said extraction zone at a point approaching but spaced from the point of withdrawal of railinate therefrom, thereby to .produc'ea high quality railinate which is substantially free of entrained naphthenes, acting on the remaining portion of the extract fraction which is not recycled with a solvent for paraf- `iinic components in a second counter iiow extraction zone to strip paraillnic components from said extract fraction, and recycling a portion of the raillnate from this second counter ilow operation in counter ilow relation with the said extract fraction during at least a substantial portion of the extraction of the latter, so as ,to-ine crease the yield of parainic-components in said raiiinate fraction.

3. In the art of separating hydrocarbon charging material into components which are'respectively more paraiiinic and more naphthenic than `the said charging material by the action of solvents, the operative process which comprises actl ing on the charging material with a solvent for one of said components in a counter iiow extraction operation involving at least one stage to produce two fractions, one of which contains most of the solvent, the hydrocarbon component more soluble therein and a small amount of the other hydrocarbon component, and the second of said fractions being composed principally o! said other or undissolved hydrocarbon component.

A acting on the mst-mentioned or dissolved i'raction in a second extraction operation with a diierent solvent having a selective solvent a!- finity for the hydrocarbon component present therein in minor amounts to separate out further quantities of the last-mentioned component, in addition to the amounts thereof produced as undissolved fraction in the iirst extraction operation. and recycling in each of said extraction operations, in counter ow relationto the hydrocarbon charge to each for at least a substantial portion of the extraction of the respective hydrocarbon charge, the product respectively of each operation which predominantly contains the solvent fed to such respective operation, thereby to secure maximum yield and quality of the desired the charging material in a firstextraction zone with a solvent for naphthenes in a counter iiow operation involving at least one stage to separate `out a rst ramnate and a rst extract.. acting on the iirst extra'et--ina second extraction zone with a solvent for parafiins in a second counter flow operation involving at least one stage to separate out a second rainate and a iinal extract, recycling a portion fof the iirst extract in the rst counter iiow operation and introducing it back paraillns is introduced thereinto, to secure a high total yield oi' raillnate. y

WARREN F. FARAGHER. 

